A Plausible Reason for Changes in El Nino Parameters in the 2000s

V. N. Stepanov

An attempt is made to find a plausible reason for the weakening of the interrelation between the variability in wind and water volume in the tropical warm pool in the western equatorial Pacific and the onset of El Nio–Southern Oscillation event (ENSO). It is demonstrated that variability in the atmospheric dynamics near the Drake Passage can affect the ENSO development. The weakening of the interrelation between ENSO and the variability in wind together with water volume in the tropical warm pool is caused by the fact that the processes of atmosphere–ocean interaction in the tropical Pacific started exerting smaller influence on the ENSO development (as compared with the processes in the Southern Ocean). This is due to warmer ocean conditions registered since the late 1990s that favored the decrease in the zonal gradient of temperature in the ocean surface layer in the tropics and led to lower atmospheric variability in the tropical Pacific whereas this variability remained the same over the Southern Ocean.